Talk:Strain wave gearing

Harmonic drive is better formatted
Perhaps this should simply redirect to Harmonic Drive (in the See Also section) as the content of the two articles is almost entirely identical, but Harmonic Drive is significantly better formatted, includes a visual, and also features citations missing from this. — Preceding unsigned comment added by 73.151.171.152 (talk) 06:40, 29 November 2016 (UTC)

Proposed merger
Harmonic drive and Strain wave gearing really need to be merged. The former article is better, but the latter is apparently the generic (non-trademark) name, so I'm proposing that the merge result live there, but obviously that's open to discussion. (Another possibility is Strain wave gear.) 209.209.238.149 (talk) 03:59, 9 February 2019 (UTC)
 * ✅ Klbrain (talk) 06:54, 21 April 2020 (UTC)

Is there anything to be said about wear or fatigue of the flexspline
Is there anything to be said about wear or fatigue of the flexspline ? How many rotations are they rated for at particular torques ? - Rod57 (talk) 11:33, 31 July 2021 (UTC)

General formula for harmonic drive axis
There should be general equation for the velocities of the three axes of a harmonic drive, because not always one of them will be fixed. Does anyone have a source on this?

I suspect it is al follows: For a fixed CS, we have $$\omega_{FS} = \frac{1}{N} \omega_{WG}$$ (N chosen by definition). When CS is not fixed, it will have some positive contribution, greater than one (because the number of teeth on the FS is smaller than on the CS). We also know that when the WG and CS have the same speed, FS will have that same speed. (I check this visually. The same teeth stay locked together in this case.) So then the ratio must be one. The unknown factor for $$\omega_{CS}$$ is then: $$1 - \frac{1}{N}$$

So then:

$$\omega_{FS} = \frac{1}{N} \omega_{WG} + \left(1 - \frac{1}{N} \right) \omega_{CS}$$

Note that $$\frac{1}{N}$$ is the reduction ratio and will be negative; $$-1 < \frac{1}{N} < 0$$

I would appreciate if anyone can confirm this! - Robert-156080 (talk) 15:03, 13 January 2022 (UTC)

—

Hm, I looked over the PDF cited for this page, which gives equations for 6 different configurations of the drive. Combining these provides the following formula:

$$\omega_{FS} = -R \omega_{WG} + \frac{R}{R + 1} \omega_{CS}$$

Note that they use reduction ratio, which is positive and smaller than 1, or $$R = -\frac{1}{N}$$ compared to my equations above.

Oddly enough, $$\frac{R}{R + 1} - R$$ is not equal to one at all. For $$0 < R < 1$$, this sum is small and negative, meaning the FS would very slowly move backwards when the CS and WG move together, which find unlikely when looking at the system.

Robert-156080 (talk) 11:26, 14 January 2022 (UTC)

-

Okay, so this PDF (https://www.harmonicdrive.net/_hd/content/documents1/FD_DifferentialGear.pdf, page 7) gives equations for differential input and the factors add up to 1. I think this is correct. This would apply the gearproductnews.com PDF is imply incorrect.

EDIT: Scratch that, the equations actually match but gearproductnews.com uses $$0 < R < 1$$ while harmonicdrive.net uses $$R > 1$$. I'll add this to the page, with clear definitions.

Robert-156080 (talk) 15:46, 14 January 2022 (UTC)